Understanding the Late Age Strength of Low CO2 Binders Incorporating Calcium Aluminates-Based Accelerators

In a previous study, it was shown that the incorporation of calcium aluminates-based accelerators is an effective solution to improve the early age strength of LC3. The higher early age strength was linked to the ettringite formation during the first hours of hydration [1]. Late age strength results (up to 1 year) of LC3 incorporating calcium aluminates-based accelerators were higher than PC and LC3. This study focuses on understanding the late age strength of LC3 boosted with calcium aluminates-based accelerators. To understand the long-term compressive strength results, thermodynamic modelling through the Gibbs energy minimisation software (GEMS) and mercury intrusion porosimetry (MIP) measurements were carried out at 28d. Thermodynamic predictions show that a higher ettringite amount is present in boosted LC3 mixes compared to LC3 system. The calculated volume fraction of the predicted phases from thermodynamic modelling shows that ettringite, C-S-H and AFm occupy 49% of the total volume while they occupy around 55% of the total volume in LC3 incorporating the calcium aluminate technology. This explains the high strength of the boosted LC3 blends. A good correlation was observed between the strength and the porosity. This demonstrates that the high late age strength comes from the reduction of porosity due to the higher volume of hydrates.